Typhoon Dujuan has howled into the southern Chinese mainland, lashing Guangdong and Hong Kong with strong winds and rain.
The darkening sky heralds the approach of the storm
But Dujuan - tipped to be the strongest typhoon this year - appears to have caused little damage despite earlier bringing chaos to Taiwan.
The Hong Kong Observatory lowered its storm alert from a second-highest Nine to an Eight on Tuesday evening, indicating winds of 63-117 kilometres per hour.
The last time the territory issued a Nine alert - meaning winds of 100 km/h - was in 1999 when Typhoon York killed two and injured 500.
Tuesday's storm uprooted at least 20 trees throughout Hong Kong and triggered two minor landslides but nobody was injured, initial reports said.
This picture of Typhoon Dujuan was sent in by Henrik Larsen, aboard the Danish ship "Heimdal" between Taiwan and Hong Kong
Chinese media have so far reported no casualties in the neighbouring province of Guangdong which was also on storm alert.
Schools there were closed down in advance and fishing boats called back to port.
"It is howling like a banshee," said one expatriate in Hong Kong, speaking from his
apartment in the Central district.
"I can actually feel the pressure building on my ears as the storm gets more intense."
Earlier, thousands of people streamed out of their buildings to catch ferries and buses home before public transport was suspended and the authorities opened temporary shelters.
People were putting tape on their windows to protect against shattered glass.
The Hong Kong stock market closed and businesses sent staff home.
Air traffic was disrupted at Hong Kong International Airport, with 151 flights cancelled and 115 delayed, officials said.
Typhoon Dujuan - the Mandarin word for the azalea flower - has a double eye.
That means the high winds could prove to be much more destructive as they twist and turn between the two centres of the storm.
The BBC's Chris Hogg in Hong Kong says that although the city's skyscrapers are built to withstand such high winds, residents on the outlying islands fear they could be in for a rough ride.
The powerful typhoon earlier lashed the southern tip of Taiwan, leaving a trail of debris and cutting electricity to more than 500,000 households. At least two people were killed.
In 2001, more than 200 people were killed in Taiwan after typhoon Toraji swept through the island.